This invention pertains to the art of cutting tools and more particularly to milling cutters.
The invention is particularly applicable to an insert type end mill and will be described with particular reference thereto. However, it will be appreciated that the invention has broader application and may be used or adapted to use with other types of cutters and in other environments where it is desired to perform a material removal operation.
There are many types and styles of end milling cutters adapted to perform different material removal functions. In a typical end mill type a plurality of cutting edges are provided which extend in a spiral or substantially spiral type of helical configuration around the cutter body with corresponding portions of the cutting edges bearing the same relationship to each other over their longitudinal extents. Some cutters have the cutting edges integrally formed on the body of the tool while others have been of the so-called insert type where a plurality of cutting tool inserts are individually affixed to a tool holder. Moreover, the entire length of each cutting edge was exposed to the workpiece at the same time so that the cutting load was continuously distributed over the entire cutting edge length. Because of this construction, the cutting or milling rates attributable to these cutters was dependent upon several factors including, for example, the number of cutting edges, the rotational speed of the cutter and the type of workpiece being processed.
Therefore, it had long been considered desirable to develop a cutting tool which would not be affected by these cutting rate factors to the same extent as conventional cutters and thereby facilitate achieving improved cutting or milling results. To that end, there have been some prior cutter developments which have met these needs and allowed better rough cutting results to be achieved. Perhaps the most successful ones of these improved cutters are those with cutting edges designed to have a generally sinusoidal or undulating configuration radially of the milling cutter. While providing improved results insofar as overall metal removal capabilities were concerned, the basic nature of the sinusoidal or undulating cutting edges is such that a relatively rough workpiece surface finish is obtained. This sometimes necessitated additional finish cutting operations.
These prior cutters also contemplated offsetting the undulations of adjacent cutting edges relative to each other for improving the cutting action, enhancing tool life and, to some degree, improving the surface finish.
Another problem with the aforementioned cutters has been that special grinding equipment was necessary to resharpen them. There have been some prior effects to eliminate these service problems by modifying the cutting edge configuration to allow more conventional resharpening. Even with such modifications, the prior cutters have suffered from those further difficulties and shortcomings noted hereinafter.
More particularly prior efforts to improve end milling cutter capabilities have involved structural arrangements constructed from high speed steel having the cutting edges integrally formed with or machined into the cutter body in a manner forming spiral helixes. High speed steel itself is limited to certain operational speeds which thus places an upper limit on the amount of improved milling results obtainable therefrom. Moreover, damage to a single one of the cutting edges in these prior structures necessitated rebuilding the cutting edge or replacement of the entire cutting tool. Both of these alternatives are time consuming and/or cost prohibitive. Other, minor damage or simple sharpening of the cutting edges required special and relatively expensive equipment which typically was not available in most small shops. Even those designed to render the cutting edges more easily serviceable suffered inherent service problems due to the basic cutting edge configurations and overall cutting tool designs.
It has, therefore, been desirable to develop an arrangement which would not only provide improved stock removal capabilities but would also overcome the aforementioned problems and difficulties. The present invention contemplates a new and improved combination and article which meet the aforementioned needs and provides a new and improved cutting tool and insert for same which is simple, economical in design and manufacture, provides substantially improved stock removal capabilities, has separate replaceable cutting edges and is readily adapted to many uses in different environments.